Homozygous hydroxymethylbilane synthase knock-in mice provide pathogenic insights into the severe neurological impairments present in human homozygous dominant acute intermittent porphyria.

Acute intermittent porphyria (AIP) is an inborn error of heme biosynthesis due to the deficiency of hydroxymethylbilane synthase (HMBS) activity. Human AIP heterozygotes have episodic acute neurovisceral attacks that typically start after puberty, whereas patients with homozygous dominant AIP (HD-AIP) have early-onset chronic neurological impairment, including ataxia and psychomotor retardation. To investigate the dramatically different manifestations, knock-in mice with human HD-AIP missense mutations c.500G>A (p.Arg167Glu) or c.518_519GC>AG (p.Arg173Glu), designated R167Q or R173Q mice, respectively, were generated and compared with the previously established T1/T2 mice with ~30% residual HMBS activity and the heterozygous AIP phenotype. Homozygous R173Q mice were embryonic lethal, while R167Q homozygous mice (R167Q+/+) had ~5% of normal HMBS activity, constitutively elevated plasma and urinary 5-aminolevulinic acid (ALA) and porphobilinogen (PBG), profound early-onset ataxia, delayed motor development and markedly impaired rotarod performance. Central nervous system (CNS) histology was grossly intact, but CNS myelination was delayed and overall myelin volume was decreased. Heme concentrations in liver and brain were similar to those of T1/T2 mice. Notably, ALA and PBG concentrations in the cerebral spinal fluid and CNS regions were markedly elevated in R167Q+/+ mice compared with T1/T2 mice. When the T1/T2 mice were administered phenobarbital, ALA and PBG markedly accumulated in their liver and plasma, but not in the CNS, indicating that ALA and PBG do not readily cross the blood-brain barrier. Taken together, these studies suggest that the severe HD-AIP neurological phenotype results from decreased myelination and the accumulation of locally produced neurotoxic porphyrin precursors within the CNS.

Severe homocysteinemia in two givosiran-treated porphyria patients: is free heme deficiency the culprit?

Givosiran is a novel approach to treat patients with acute intermittent porphyrias (AIP) by silencing of ∂-ALA-synthase 1, the first enzyme of heme biosynthesis in the liver. We included two patients in the Envision study who responded clinically well to this treatment. However, in both patients, therapy had to be discontinued because of severe adverse effects: One patient (A) developed local injection reactions which continued to spread all over her body with increasing number of injections and eventually caused a severe systemic allergic reaction. Patient B was hospitalized because of a fulminant pancreatitis. Searching for possible causes, we also measured the patients plasma homocysteine (Hcy) levels in fluoride-containing collection tubes: by LC-MS/MS unexpectedly, plasma Hcy levels were 100 and 200 in patient A and between 100 and 400 µmol/l in patient B. Searching for germline mutations in 10 genes that are relevant for homocysteine metabolism only revealed hetero- and homozygous polymorphisms in the MTHFR gene. Alternatively, an acquired inhibition of cystathionine-beta-synthase which is important for homocysteine metabolism could explain the plasma homocysteine increase. This enzyme is heme-dependent: when we gave heme arginate to our patients, Hcy levels rapidly dropped. Hence, we conclude that inhibition of ∂-ALA-synthase 1 by givosiran causes a drop of free heme in the hepatocyte and therefore the excessive increase of plasma homocysteine. Hyperhomocysteinemia may contribute to the adverse effects seen in givosiran-treated patients which may be due to protein-N-homocysteinylation.

Dysregulation of homocysteine homeostasis in acute intermittent porphyria patients receiving heme arginate or givosiran.

Acute intermittent porphyria (AIP) is a rare metabolic disease caused by mutations within the hydroxymethylbilane synthase gene. Previous studies have reported increased levels of plasma total homocysteine (tHcy) in symptomatic AIP patients. In this study, we present long-term data for tHcy and related parameters for an AIP patient cohort (n = 37) in different clinical disease-states. In total, 25 patients (68%) presented with hyperhomocysteinemia (HHcy; tHcy > 15 µmol/L) during the observation period. HHcy was more frequent in AIP patients with recurrent disease receiving heme arginate, than in nonrecurrent (median tHcy: 21.6 µmol/L; range: 10-129 vs median tHcy: 14.5 µmol/L; range 6-77). Long-term serial analyses showed a high within-person tHcy variation, especially among the recurrent patients (coefficient of variation: 16.4%-78.8%). HHcy was frequently associated with low blood concentrations of pyridoxal-5'-phosphate and folate, while cobalamin concentration and the allele distribution of the methylene-tetrahydrofolate-reductase gene were normal. Strikingly, 6 out of the 9 recurrent patients who were later included in a regime of givosiran, a small-interfering RNA that effectively reduced recurrent attacks, showed further increased tHcy (median tHcy in 9 patients: 105 µmol/L; range 16-212). Screening of amino acids in plasma by liquid-chromatography showed co-increased levels of methionine (median 71 µmol/L; range 23-616; normal <40), suggestive of acquired deficiency of cystathionine-ß-synthase. The kynunerine/tryptophan ratio in plasma was, however, normal, indicating a regular metabolism of tryptophan by heme-dependent enzymes. In conclusion, even if HHcy was observed in AIP patients receiving heme arginate, givosiran induced an aggravation of the dysregulation, causing a co-increase of tHcy and methionine resembling classic homocystinuria.

5-Aminolevulinate dehydratase porphyria: Update on hepatic 5-aminolevulinic acid synthase induction and long-term response to hemin.

BACKGROUND: 5-Aminolevulinic acid dehydratase (ALAD) porphyria (ADP) is an ultrarare autosomal recessive disease, with only eight documented cases, all of whom were males. Although classified as an acute hepatic porphyria (AHP), induction of the rate limiting hepatic enzyme 5-aminolevulinic acid synthase-1 (ALAS1) has not been demonstrated, and the marrow may also contribute excess 5-aminolevulinic acid (ALA). Two patients have died and reported follow up for the others is limited, so the natural history of this disease is poorly understood and treatment experience limited. METHODS: We report new molecular findings and update the clinical course and treatment of the sixth reported ADP patient, now 31 years old and the only known case in the Americas, and review published data regarding genotype-phenotype correlation and treatment. RESULTS: Circulating hepatic 5-aminolevulinic acid synthase-1 (ALAS1) mRNA was elevated in this case, as in other AHPs. Gain of function mutation of erythroid specific ALAS2 - an X-linked modifying gene in some other porphyrias - was not found. Seven reported ADP cases had compound heterozygous ALAD mutations resulting in very low residual ALAD activity and symptoms early in life or adolescence. One adult with a germline ALAD mutant allele developed ADP in association with a clonal myeloproliferative disorder, polycythemia vera. CONCLUSIONS: Elevation in circulating hepatic ALAS1 and response to treatment with hemin indicate that the liver is an important source of excess ALA in ADP, although the marrow may also contribute. Intravenous hemin was effective in most reported cases for treatment and prevention of acute attacks of neurological symptoms.

Pilot study of mitochondrial bioenergetics in subjects with acute porphyrias.

BACKGROUND AND AIMS: The acute porphyrias are characterized by defects in heme synthesis, particularly in the liver. In some affected patients, there occurs a critical deficiency in a regulatory heme pool within hepatocytes that leads to up-regulation of 5-aminolevulinic acid [ALA] synthase-1, which is the first and normally rate-controlling enzyme in the pathway. In earlier work, we described defects in mitochondrial functions in cultured skin fibroblasts from patients with acute intermittent porphyria [AIP]. Others described defects in livers of murine models of AIP. Here, we explored mitochondrial energetics in peripheral blood mononuclear cells [PBMCs] and platelets in persons with AIP and hereditary coproporphyria [HCP]. Our hypotheses were that there are deficits in bioenergetic capacity in acute porphyrias and that subjects with more severe acute porphyria have more pronounced reductions in mitochondrial oxygen consumption rates [OCR]. METHODS: We studied 17 subjects with acute hepatic porphyrias, 14 with classical AIP, one with severe AIP due to homozygous deficiency of hydroxymethylbilane synthase [HMBS], 2 with HCP, and 5 non-porphyric controls. We collected peripheral blood, isolated PBMCs, which we assayed either immediately or after frozen storage [80C] for up to 14 days. Using Seahorse XF-24-3, we measured OCR in the presence of glucose + pyruvate under basal condition, and after additions of oligomycin, carbonylcyanide p-trifluoromethoxyphenylhydrazone [FCCP], and antimycin+rotenone. RESULTS: Most subjects [13/17, 76%] were female. Subjects with moderate/severe symptoms associated with acute porphyria had significantly lower basal and maximal-OCR than those with no/mild symptoms who were the same as controls. We observed significant inverse correlation between urinary porphobilinogen [PBG] excretion and OCR. The subject with homozygous AIP had a much lower-OCR than his asymptomatic parents. SUMMARY/CONCLUSIONS: Results support the hypothesis that active acute hepatic porphyria is characterized by a deficiency in mitochondrial function that is detectable in PBMCs, suggesting that limitations in electron transport and ATP production exist in such individuals.

Sex differences in vascular reactivity in mesenteric arteries from a mouse model of acute intermittent porphyria.

BACKGROUND AND AIMS: Acute intermittent porphyria (AIP) results from a partial deficiency of porphobilinogen deaminase (PBGD). Symptomatic AIP patients, most of whom are women, experience acute attacks characterized by severe abdominal pain and abrupt increases in blood pressure. Here, we characterized the reactivity of mesenteric arteries from male and female AIP mice with ~30% of normal PBGD activity and wild type C57BL/6 mice. METHODS: An acute porphyric attack was induced in AIP mice by treatment with phenobarbital. Vascular responses to K+, phenylephrine (PE), acetylcholine (ACh), and hemin were determined (Wire Multi Myograph). RESULTS: Maximal contraction to PE was increased in arteries from male and female AIP mice (p < .05) during an induced attack of acute porphyria. Female AIP arteries had increased sensitivity to PE (p < .05) even after nitric oxide (NO) blockade with Nω-nitro-L-arginine methyl ester (L-NAME) (p < .05). Maximal relaxation to ACh was similar in males and females with lower sensitivity in female AIP arteries (p < .05). Hemin induced greater relaxation in AIP arteries in both males and females (p < .05). SUMMARY/CONCLUSIONS: Sex differences in this AIP mouse model include a pro-contractile response in females. These alterations may contribute to the increased blood pressure during an acute attack and provide a novel mechanism of action whereby heme ameliorates the attacks.

Glucose metabolism during fasting is altered in experimental porphobilinogen deaminase deficiency.

Porphobilinogen deaminase (PBGD) haploinsufficiency (acute intermittent porphyria, AIP) is characterized by neurovisceral attacks when hepatic heme synthesis is activated by endogenous or environmental factors including fasting. While the molecular mechanisms underlying the nutritional regulation of hepatic heme synthesis have been described, glucose homeostasis during fasting is poorly understood in porphyria. Our study aimed to analyse glucose homeostasis and hepatic carbohydrate metabolism during fasting in PBGD-deficient mice. To determine the contribution of hepatic PBGD deficiency to carbohydrate metabolism, AIP mice injected with a PBGD-liver gene delivery vector were included. After a 14 h fasting period, serum and liver metabolomics analyses showed that wild-type mice stimulated hepatic glycogen degradation to maintain glucose homeostasis while AIP livers activated gluconeogenesis and ketogenesis due to their inability to use stored glycogen. The serum of fasted AIP mice showed increased concentrations of insulin and reduced glucagon levels. Specific over-expression of the PBGD protein in the liver tended to normalize circulating insulin and glucagon levels, stimulated hepatic glycogen catabolism and blocked ketone body production. Reduced glucose uptake was observed in the primary somatosensorial brain cortex of fasted AIP mice, which could be reversed by PBGD-liver gene delivery. In conclusion, AIP mice showed a different response to fasting as measured by altered carbohydrate metabolism in the liver and modified glucose consumption in the brain cortex. Glucose homeostasis in fasted AIP mice was efficiently normalized after restoration of PBGD gene expression in the liver.

Systemic inflammation in acute intermittent porphyria: a case-control study.

This study aimed to examine whether acute intermittent porphyria (AIP) is associated with systemic inflammation and whether the inflammation correlates with disease activity. A case-control study with 50 AIP cases and age-, sex- and place of residence-matched controls was performed. Plasma cytokines, insulin and C-peptide were analysed after an overnight fast using multiplex assay. Long pentraxin-3 (PTX3) and complement activation products (C3bc and TCC) were analysed using enzyme-linked immunosorbent assay (ELISA). Urine porphobilinogen ratio (U-PBG, µmol/mmol creatinine), haematological and biochemical tests were performed using routine methods. Questionnaires were used to register AIP symptoms, medication and other diseases. All 27 cytokines, chemokines and growth factors investigated were increased significantly in symptomatic AIP cases compared with controls (P < 0·0004). Hierarchical cluster analyses revealed a cluster with high visfatin levels and several highly expressed cytokines including interleukin (IL)-17, suggesting a T helper type 17 (Th17) inflammatory response in a group of AIP cases. C3bc (P = 0·002) and serum immunoglobulin (Ig)G levels (P = 0·03) were increased significantly in cases with AIP. The U-PBG ratio correlated positively with PTX3 (r = 0·38, P = 0·006), and with terminal complement complex (TCC) levels (r = 0·33, P = 0·02). PTX3 was a significant predictor of the biochemical disease activity marker U-PBG in AIP cases after adjustment for potential confounders in multiple linear regression analyses (P = 0·032). Prealbumin, C-peptide, insulin and kidney function were all decreased in the symptomatic AIP cases, but not in the asymptomatic cases. These results indicate that AIP is associated with systemic inflammation. Decreased C-peptide levels in symptomatic AIP cases indicate that reduced insulin release is associated with enhanced disease activity and reduced kidney function.

[Plasma and salivary markers of oxidative and carbonyl stress in patients with acute intermittent porphyria]. / Markery oxidacného a karbonylového stresu v plazme a slinách u chorých s akútnou intermitentnou porfýriou.

BACKGROUND: Acute intermittent porphyria (AIP) is an autosomal inherited disease caused by deficiency of the third enzyme in the heme biosynthetic pathway, porphobilinogen deaminase. The clinical course of the disease is characterized by acute attacks, most often with abdominal pain.The aim of our study was to investigate selected markers of oxidative and carbonyl stress in plasma and saliva in patients with AIP and to find out whether saliva could be used for monitoring the disease progression. Saliva is an attractive biological fluid for determination of biochemical markers in various pathological conditions. The advantage is that saliva can be collected non-invasively, and the examination needs only a small volume of saliva. METHODS: Blood and total non-stimulated saliva were collected from 16 patients with AIP in remission, and from 20 healthy individuals. Markers of oxidative and carbonyl stress - advanced glycation end products (AGEs), and thiobarbituric acid reacting substances (TBARS) were determined by spectrofluorometric methods, advanced oxidation protein products (AOPPs), total antioxidant capacity (TAC) and ferric reducing ability of plasma/saliva (FRAP/FRAS) were investigated by spectrophotometric methods in the above mentioned groups. RESULTS: Advanced glycation end products and thiobarbituric acid reacting substances in plasma and saliva were significantly higher in patients with AIP in comparison to the control group (p < 0.001) and (p < 0.05). Advanced oxidation protein products in AIP if compared to the control group did not show statistical significance (p > 0.05), but the levels in the saliva were significantly lower (p < 0.001). The concentrations of markers of antioxidant status of plasma and saliva were significantly lower in AIP if compared to the control group (p < 0.001). CONCLUSIONS: According to the best of our knowledge this is the first study to demonstrate increased concentrations of markers of oxidative and carbonyl stress and decreased antioxidant status of plasma and saliva in patients with AIP. Moreover, the study suggests that the saliva might be a promising fluid to study relevant biomarkers in a wide array of human biomedical conditions.Key words: acute intermittent porphyria - biomarkers - oxidative and carbonyl stress - plasma and saliva.

An odd case of heteroallelic acute intermittent porphyria in the Argentinean population.

AIP is an acute liver disorder caused by a deficiency of porphobilinogen deaminase (PBGD) characterized by neuroabdominal symptoms. It is an autosomal dominant disease. However, homozygous dominant AIP (HD-AIP) have been described. In some cases erythrodontia was observed. CEP is an autosomal recessive disease produced by mutations in the uroporphyrinogen III synthase gene (UROS), characterized by severe cutaneous lesions and erythrodontia. The aim of the work was to establish the differential diagnosis of porphyria in a patient with abdominal pain, neurological attacks, skin symptoms and erythrodontia. The PBGD activity was reduced 50% and the genetic analysis indicated the presence of two genetic variants in the PBGD gene, p.G111R and p.E258G, a new genetic variant, revealing a case of heteroallelic HD-AIP. The patient, first diagnosed as a carrier of a dual porphyria: AIP / CEP based on the excretion profile of porphyrins, precursors and her clinical symptoms, would be an atypical case of human HD-AIP. These results would also suggest the presence of a phenocopy of the CEP, induced by an endogenous or exogenous factor. Our findings highlight the importance of genetic studies for a proper diagnosis of porphyria, prevention of its manifestation and its treatment.

Direct and simultaneous quantitation of 5-aminolaevulinic acid and porphobilinogen in human serum or plasma by hydrophilic interaction liquid chromatography-atmospheric pressure chemical ionization/tandem mass spectrometry.

Serum/plasma concentrations of 5-aminolaevulinic acid (ALA) and porphobilinogen (PBG) are elevated in patients with acute hepatic porphyrias, especially during acute attacks. Current assays require lengthy sample pre-treatment and derivatization steps. We report here a rapid, sensitive and specific hydrophilic interaction liquid chromatography-tandem mass spectrometry method for the direct and simultaneous quantitation of ALA and PBG in serum or plasma following simple protein precipitation with acetonitrile and centrifugation prior to injection. ALA and PBG were detected using selected reaction monitoring mode, following positive atmospheric pressure chemical ionization. Calibration was linear from 0.05 to 50 µmol/L for ALA and PBG. For both analytes, imprecision (relative standard deviation) was <13% and accuracy (percentage nominal concentrations) was between 92 and 107%. The method was successfully applied to the measurement of ALA and PBG in serum or plasma samples for the screening, biochemical diagnosis and treatment monitoring of patients with acute hepatic porphyrias.

Biochemical and hematological analysis in acute intermittent porphyria (AIP): a case report.

Acute intermittent porphyria is the most common acute porphyria caused by a decrease in hepatic porphobilinogen deaminase activity, resulting in an accumulation of delta-aminolevulinic acid and porphobilinogen. This disease shows nonspecific signs and symptoms that can be confused with other diseases, thereby making the diagnosis difficult. We report a case of acute intermittent porphyria, reviewing clinical and laboratory aspects, highlighting the hematological and biochemical parameters during and after the crisis. A female patient, aged 28 years, suffered two crises, both presenting gastrointestinal disorders. The second presented neuropsychiatric symptoms. The analysis of hematological and biochemical parameters during the second crisis showed anemia, leukocytosis, hyponatremia, mild hypokalemia, uremia and elevated C-reactive protein. The initial treatment included glucose infusion, a diet rich in carbohydrates and interruption of porphyrinogenic drugs. Subsequently, treatment was maintained with oral contraceptive use. According to the observed data, signs and symptoms of gastrointestinal, neurological and psychiatric disorders, associated with laboratory results presented in this paper can be applied to screen acute porphyria, contributing to early diagnosis.

Women with acute intermittent porphyria have a defect in 5α-steroid production during the menstrual cycle.

OBJECTIVE: To measure serum concentrations of progesterone, estradiol and 5α- and 5ß-reduced progesterone metabolites in the follicular and luteal phases of the menstrual cycle in women with latent acute intermittent porphyria and manifest acute intermittent porphyria in comparison with healthy control women. DESIGN: A descriptive study with repeated measurements during a complete, ovulatory menstrual cycle. SETTING: University hospital out-patient clinic. POPULATION: Thirty-two women with DNA-diagnosed acute intermittent porphyria and 20 healthy control women. METHODS: Blood samples for serum progesterone, estradiol, allopregnanolone and pregnanolone were drawn on predefined menstrual cycle days, twice in the follicular phase and three times in the luteal phase. Serum levels of estradiol and progesterone were analysed with commercial kits. Allopregnanolone and pregnanolone levels were analysed with radioimmunoassay following diethylether extraction and celite column chromatography. MAIN OUTCOME MEASURES: Changes in serum levels of progesterone, estradiol, allopregnanolone and pregnanolone throughout the menstrual cycle. RESULTS: Women with acute intermittent porphyria displayed lower serum concentrations of allopregnanolone in comparison with healthy control women, the difference being most prominent in the luteal phase (p < 0.001). Levels of pregnanolone did not differ significantly between groups. No significant difference was found between women with latent acute intermittent porphyria and manifest acute intermittent porphyria. CONCLUSIONS: Decreased levels of the 5α-reduced progesterone metabolite allopregnanolone were found in the menstrual cycle of women with acute intermittent porphyria. This has not been reported previously and could indicate a reduced 5α-reductase type 1 capacity in the ovary and liver among these women.

[Toxic effects of cadmium on the human body (literature review)].

A review of the literature about the toxic effects of cadmium on the human body. We describe a patient with clinical and biochemical signs of an attack of acute porphyria imitated or severe lead poisoning. In the patient's blood was revealed a 3-fold, compared to the allowable rate, increase of cadmium in the normal lead content. We discuss the etiologic role of cadmium and the possible pathogenetic mechanisms of this pathological condition.

Kidney damage in acute intermittent porphyria.

BACKGROUND: Acute intermittent and variegate porphyria are an autosomal dominant hereditary diseases caused by the deficient activity of porphobilinogen deaminase in the haem biosynthesis. Acute intermittent porphyria (AIP) in 11 patients (8 women and 3 men) and variegate porphyria (VP) in one patient were diagnosed and long-term treated during 15-22 years. Eleven patients had in acute attack abdominal pain, they were agitated and restless and suffered from insomnia. Besides they had various neurological signs. Examination of kidney function during remission showed hypertension and tubulointerstitial impairment of the kidneys in 10 patients (hyposthenuria and impairment of tubular excretory phase in isotopic renography). Deficiency of serum erythropoietin in 4 patients, significant deficiency of plasma and erythrocyte vitamin B6, significant hyperoxalaemia and hyperoxaluria in all patients were found. Direct relationship between plasma oxalic acid and effect of pyridoxal-5-phosphate (PLP), (effect of PLP was in indirect relationship with the concentration of erythrocyte vitamin B6), in AIP patients was found. Deficiency of vitamin B6 was probably a cause of hyperoxalaemia and hyperoxaluria in those patients. The effective therapy was repeated i.v. administration of haem-arginate during acute attacks (4-5 days). Besides during remission the patients were treated by pyridoxine (40-60 mg/day), by glucose, sodium chloride and phenothiazines. All patients showed significant improvement and had regular ambulatory check-up every three months. Currently, they are in clinical and laboratory remission.

Vitamin B6 and oxalic acid in clinical nephrology.

OBJECTIVE: Vitamin B(6) (VB(6)) is a water-soluble vitamin, which is important for the normal functioning of multiple organ systems. It is metabolized to the active molecule pyridoxal-5-phosphate (PLP). Oxalic acid (OA) is thought to be a uremic toxin that participates in the pathogenesis of the uremic syndrome. The objectives of this study were as follows: (1) to evaluate the plasma and erythrocyte VB(6) (effect of PLP; effect of PLP was in indirect relationship with the concentration of erythrocyte VB(6)), and plasma and urinary OA in marathon runners, in patients with acute intermittent porphyria (AIP) and variegate porphyria, and in patients with stage 1 chronic kidney disease (CKD), chronic glomerulonephritis and nephrotic syndrome (CGNS); (2) to examine the influence of water diuresis in healthy subjects, and the influence of sodium diuresis (high sodium intake) and an intravenous administration of furosemide on the urinary excretion of VB(6) and OA in CKD stage 3-4 patients; and (3) to evaluate the influence of erythropoietin treatment on erythrocyte VB(6) (effect of PLP) in hemodialysis (HD) patients, and the influence of continuous ambulatory peritoneal dialysis (CAPD) therapy on plasma VB(6) and OA and their peritoneal clearance and transfer. DESIGN AND SETTING: This study was conducted at the Nephrological Clinic of L. Pasteur Faculty Hospital and of Medical School of P. J. Safarik University. A combination of 29 marathon runners, 15 patients with CG and NS, 11 patients with AIP, 1 patient with variegate porphyria, 15 healthy subjects, 27 CKD stage 3-4 patients, 30 HD, and 27 CAPD patients were used in the study. RESULTS: After a marathon run, plasma and erythrocyte VB(6) significantly decreased and plasma OA increased. Plasma (15.5 +/- 3.8 nmol/L) and erythrocyte VB(6) (effect of PLP: 42.1% +/- 7.5%) were decreased and plasma OA (9.8 +/- 2.3 micromol/L) was significantly elevated in patients with CGNS and stage 1 CKD. In patients with AIP, deficiency of plasma (24.3 +/- 5.2 nmol/L) and erythrocyte VB(6) (effect of PLP: 46.2% +/- 7.0%) and hyperoxalemia (9.39 +/- 2.5 micromol/L) were present. The urinary excretion of VB(6) and of OA during maximal water diuresis and after intravenous administration of furosemide increased significantly (P < .01), but was not affected by the high intake of NaCl (P > .05). Erythropoietin treatment in HD patients led to the erythrocyte VB(6) deficiency. This finding is an indirect evidence that erythrocyte VB(6) is consumed by the hemoglobin synthesis much more during EPO treatment. In CAPD patients, plasma value of VB(6) (127.3 +/- 66.9 micromol/L) was in the normal range and plasma OA (23.6 +/- 7.4 micromol/L) was significantly elevated. Mean value of peritoneal clearance of VB(6) was 8.8% and of OA was 76.9% of urea clearance. CONCLUSION: Our study indicates that deficiency of VB(6) led to hyperoxalemia and hyperoxaluria in patients with CKD. Deficiency of VB(6) in CKD stage 4-5 patients potentiates the uremic hyperoxalemia and hyperoxaluria.

Role of two nutritional hepatic markers (insulin-like growth factor 1 and transthyretin) in the clinical assessment and follow-up of acute intermittent porphyria patients.

OBJECTIVE: Acute intermittent porphyria (AIP) is caused by a deficiency of hydroxymethylbilane synthase. Clinical manifestations are abdominal pain and neurovisceral symptoms, accompanied by overproduction of heme-precursors in the liver, which frequently remains long-lasting in AIP patients. We tested the hypothesis that this condition may be associated with alterations of hepatic proteins known to be either increased or decreased in serum according to diverse pathological conditions including malnutrition, inflammation or liver disease. DESIGN: Serum proteins were analyzed in 26 biochemically active AIP patients that were classified according to the EPI (European Porphyria Initiative) guidelines as follows: (i) patients who presented a single acute attack having remained so far free of clinical symptoms; (ii) patients who present recurrent attacks or chronic symptoms associated with exacerbations of AIP. RESULTS: Most of the serum proteins were within normal limits, however insulin-like growth factor 1 (IGF-1) was decreased in 53.8% of AIP patients (z-score = -2.86 +/- 0.37) and transthyretin (prealbumin) was found significantly decreased in 38.5% of them. The IGF-1 z-score was lower in group B versus group A patients (-2.66 vs. -1.43; P = 0.024). The coincident decrease of both IGF-1 and transthyretin was associated with worsening of the clinical condition. CONCLUSIONS: This first study in humans suggests that the clinical expression AIP is associated with a state of under-nutrition and/or with hepatic inflammation due to the sustained accumulation of heme-precursors. We propose the use of both IGF-1 and transthyretin as biomarkers of disease morbidity/severity for the clinical follow-up of AIP patients.

Nerve function and dysfunction in acute intermittent porphyria.

Acute intermittent porphyria (AIP) is a rare metabolic disorder characterized by mutations of the porphobilinogen deaminase gene. Clinical manifestations of AIP are caused by the neurotoxic effects of increased porphyrin precursors, although the underlying pathophysiology of porphyric neuropathy remains unclear. To further investigate the neurotoxic effect of porphyrins, excitability measurements (stimulus-response, threshold electrotonus, current-threshold relationship and recovery cycle) of peripheral motor axons were undertaken in 20 AIP subjects combined with the results of genetic screening, biochemical and conventional nerve conduction studies. Compared with controls, excitability measurements from five latent AIP patients were normal, while 13 patients who experienced acute porphyric episodes without clinical neuropathy (AIPWN) showed clear differences in their responses to hyperpolarizing currents (e.g. reduced hyperpolarizing I/V slope, P < 0.01). Subsequent mathematical simulation using a model of human axons indicated that this change could be modelled by a reduction in the hyperpolarization-activated, cyclic nucleotide-dependent current (I(H)). In contrast, in one patient tested during an acute neuropathic episode, axons of high threshold with reduced superexcitability, consistent with membrane depolarization and reminiscent of ischemic changes. It is proposed that porphyrin neurotoxicity causes a subclinical reduction in I(H) in AIPWN axons, whereas porphyric neuropathy may develop when reduced activity of the Na(+)/K(+) pump results in membrane depolarization.